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Patented Jan. 27, 1931 UNITED STATES PATENT OFFICE ELLERY H. HARVEY, ,OFLANSDALE, iENNSYLVANIA, ASSIGNOR T PERKINS GLUE I COMPANY, ACOIRZPORATION OF DELAWARE rnocnss or MAKING VEGETABLE GLUE My inventionrelates to improvements in rying out the factory control method, the

processes of making vegetable glue and more particularly vegetable gluehaving substantially the adhesive properties of animal veneering glue.

It has been common for many years to make vegetable glue for furnitureveneering by dissolvingone part starch in about 3 parts or less byweight of water with caustic alkali such as caustic soda which acts as asolvent of the starch in water. Sometimes a partially hydrolyzedordegenerated starch is used and sometimes a starch just as it comes onthe market is used, cassava starch, or

tapioca flour as it is sometimes called, being preferred. See U. S.Reissued Letters Pats ent 13,436 granted July 2, 1912. As thereindescribed the starch may be dissolved at or-.

dinary temperature or a carefully regulated heat (preferably below 175F.) may be used, the amount of caustic solvent used being less when heatis used in dissolving.

The starches more commonly used (whether partially hydrolyzed or not)have been such that the resulting glue has had a specific viscosity of]80,000 or more; A glue havinga viscosity of about 80,000 I'believe to bethe best for all around furniture veneering. 'lhe viscosity may besomewhatv greater without greatly aflecting the workability of the gluebut I prefer that it be not over 175,000.

Such an increase in viscosity is not so disadvantageous as a viscositymaterially below 80,000. These viscosity figures represent the specificviscosity of the glue as compared with that of water at 20 C. and aremeasured when the glue is at substantially 75 F. and

- may be measured by an apparatus andin a not represent the sameviscosities as would be obtained upon glue made up in a large kettle asemployed for factory conversion. In car- Application (filed September19, 1923. Serial No; 663,713.

specific procedure is preferably employed as follows :814 cc, of waterare placed in a kettle geared to run 84 'R. P. M., 400 rams of flourhaving a moisture content of is spun and agitation continued for about 5i to 16% are added, the agitator in the kettle minutes. Add 36 cc. of 3to l C. P. caustic soda solution,,taking 5 minutes to add it. Turn onthe steam in the kettle carefully so that the glue is gradually andsmoothly converted to 170 F. taking 20 minutes to bring of water wouldproduce a glue having a viscosity of 80,000 or more. For-this purpose ithas been necessary to select the so-called high grade starches (such asthe high grade cassava starches) which starches are the more expensive.When it has been attempted to make the glue from the lower grade or lessexpensive starches, and particularly low grade cassava, in the mannerabove set forth it is found that the viscosity of the resulting glue,even if as little as 2 parts of water be used, is materiallybelow 80,000and while the glue has considerable adhesiveness, it is sloppy anddiflicult to apply with the spreading machines commonly used to applythe same in furniture veneering. It is diflicult if not impossibletoapply it to the wood veneer layersevenly and in proper quantity,Itfrequently slops oil the spreading rolls and wood veneer sheets ontothe floor causing a very considerable loss of glue as well asadding tothe labor necessary to keep the factory clean and in proper order. Theglue also slops ofi onto the hands of the workmen increasing thedificulties of handling the machines and wood veneers and making thework very disagreeable. Finally such a low viscosity glue is likely topenetrate, too readily into porous parts of the wood or any soft porouskinds of wood and make unreliable joints.

According to my invention I use such cheap, low grade, low viscositystarch, but avoid the disadvantages above pointed out by adding acoagulating agent to increase the viscosity of the resulting glue to80,000 or more whereby the sloppy characteristic of the glue is removedand the glue is substantially the same in its adhesive qualities andworkability as if made with the higher grade starches as above pointedout.

I am aware that it has been suggested that coagulating agents may beadded to different vegetable glues for different purposes. It has beensuggested that more economy might be obtained with the high grade, highpriced starches by increasing the water in the glue made therefrom to,say, from 4 to 7 parts of water and then, in order to counteract thetendency of the increased water to make the glue too fluid, coagulatingor thickening agents have been added. In this way a given amount ofstarch will produce a great deal more glue which may be spread over agreat deal more surface thus considerably decreasing the glue cost for agiven area glued. But such glue is disadvantageous particularly withsome classes of work, in that the water has to be almost entirely driedout in producing the glued joint, and the increased water increases thedrying time, and tends to warp the wood veneers and produce weak oints,all of very serious consequence.

It has also been suggested that great economy might be obtained by usingthese high grade, high priced starches (which Without any coagulatingagent produce glues in the manner above described having a viscosity of80,000 or over) and using a coagulating agent therewith to increase theviscosity of the l esulting glue very greatly above 80,000. For examplethe addition of the coagulating agent in such case might increase theviscosity of the glue from say 90,000 to 100,000 to 150,000 or 200,000.With such a heavy viscous glue, the glue penetrates the wood less and itwas supposed therefore that it might be spread much thinner andtherefore a greater area may be glued with a given amount of glue orstarch and thus greater economy obtained. I have found, however, thatfor good reliable joints in furniture work this method of seekingeconomy is not satisfactory and I believe it to be because too littledry material is finally left in the joints. For certain classes of work,some consider such a glue to have a better consistency. Such a glue,however, has the disadvantage that it is more difficult to handle in theglue mixing and spreading apparatus.

So far as I am aware, in all cases where a coagulating agent has beenused, it has been in a glue, the starch in which would produce withoutthe coagulating agent and with 2 parts of water, a glue having aviscosity of 80,000 or more, and the high grade, higher priced cassavastarches were used, and economy was attempted by increasing the spreadper unit of starch used.

In contradistinction thereto, I use the low grade or low priced starcheswhich when dissolved in 2 parts of water by mixing the starch with theWater and 8% of caustic soda and heating to 170 F. and continuing theheating with agitation until the starch has been dissolved to produce afluent glue, without any coagulating agent would produce a glue havinga. viscosity below 80,000 and I overcome any sloppy tendency andincrease the viscosity thereof by the addition of a coagulating agent,and I obtain greater economy by using a less expensive starch as'a baseinstead of by increased spread per unit of high grade starch. Also Ithus avoid the use of so much water as to retard the time of drying andrisk of injury to the wood, but materially more than 3 parts of watermay be used in some classes of work. -I also fully maintain the'desiredquantity of dry material in the final joint. In this manner I am able toobtain a long sought improvement in economy without danger of injury tothe quality of the joint.

By coagulating agent I mean any chemical or chemicals or medium whichserves to cause the viscosity of the glue to be increased. Manydifferent salts may be used for this purpose for example salts of theamphoteric polyvalent metals such as iron sulphate FesO tin chloride,nickel chloride, etc. or ,borax or certain of the natural oxids orphosphates which may be present in starch, but I prefer touse the ironsulphate because of its availability and cheapness.

The coagulating agent may be thoroughly mixed with the starch before itis mixed with the water and dissolved. In this way by adjusting theamount of coagulating agent to the particular starch being used, astarch base of uniform viscosity may be easily produced. Or thecoagulating agent may be added to the mixture of starch and water andmixed therewith before the solvent is added to dissolve the starch; orit may be added while the glue is being dissolved, or, in some casesafter it has been dissolved. By solvent I mean any agent which aids indissolving the starch in water. In some cases solvents other thancaustic soda or caustic alkali may be used, such as trisodium phosphate.sodium aluminate, tribasic acetate of lead, formaldehyde etc. (see U. S.Letters Patent 1,378,105), but the solvent should be non-acid incharacter to give the best results with most of the coagulating agents Iprefer to use because of their cheapness. When the coagulating agent ismixed with the starch by hand it may be added thereto in dry form or maybe sprayed on the dry starch in the form of a solution, the

'if desired.

Generally only a small amount of coagulating agent is required so thatthe expense thereof is inconsiderable. For example, with a certain cheapgrade of cassava starch I found that the viscosity of glue at 75 F. madetherewith by dissolving it in 2 parts of water with 3% of caustic sodaand heating the batch to 170 F. and continuing the heat with agitationuntil the starch was dissolved to produce a fluent glue, was 44,000. Byadding two-tenths of one per cent (2%) of iron sulphate (FeSO theviscosity of the resulting glue was increased to 80,000. By using onequarter of one per cent of iron sulphate the viscosity was increased to138,000. The iron sulphate was added and stirred in when the be addedbefore or after.

' mined by similar experimental testing. The

particular viscosity to which the glue should be increased will varysomewhat according to the conditions under which the glue is to be usedor purposes for which it is to be used, but generally speaking I preferto add such a quantity of coagulent as will increase the, viscosity ofthe resulting glue from under 60,000 to over 60,000.

The expression starch of a specific viscosity less than 60,000 employedin the claims refers to a starch which when dissolved and testedaccording to the procedure for determining viscosities above set forth,will indicate a viscosity of the figure mentioned. 7

What I claim as new and desire to secure by Letters Patent, is:

1. The process of making vegetable glue suitable without dilution forgeneral furniture veneering which comprises dissolving one part ofstarch of a specific viscosity less than 60,000 in about three parts orless of water with an alkaline solvent inthe presence of a suflicientquantity of an iron compound for increasing the viscosity to form a uentglue with a specific viscosity of at least about 80,000.

2. The process of making vegetable glue suitable without dilution forgeneral furniture veneering which comprises dissolving one part ofcassava starch of a specific viscosity less than 60,000 in about threeparts or less of water with about 3% of cautic soda and heating thebatch to about 170 F. in the presence of an iron salt to form a fluentglue with a specific viscosity of at least about 80,000.

3,. The process of making vegetable glue suitable without dilution forgeneral furniture veneering which comprises dissolving one part ofcassava starch of a specific viscosity less than 60,000 in about threeparts or less of water with about 3% of caustic soda and heating thebatch to about 17 0 F. in the presence of ferrous sulphate to form afluent glue with a specific viscosity of at least about 80,000.

4. A fluent vegetable glue suitable without dilution for generalfurniture veneering having a specific viscosity of about at least 80,000prepared by dissolving about one part of cassava starch of a specificviscosity less than 60,000 in about three parts or less of water withabout 3% of cautic soda and heating the batch to about 17 0 F. in thepresence of an iron salt.

In testimony whereof I have signed my

